Control system



R. M. HARDGROVE CONTROL SYSTEM Dec. 2 7, 1938.

2 Sheets-sheaf. 1

Original Filed May 8, l931 v De'c. 27, 1938. I R, M HARDGRQVE 2,141,604

CONTROL SYSTEM Original Filed May 8, 1951 2 Sheets-Sheet 2 mvsmon.

Ralph M. Harq r'ove Patented Dec. 27, 1938 UNITED STATES PATENT OFFICE to Bailey Meter Company,

Delaware a corporation oi Original application May 8, 1931, 'Serial No. 536,037. Divided and this application June 25,

1935, Serial No. 28,382

9 Claims. (Cl. 110-106) This invention relates to automatic control systems for pulverizing mills, and more particularly to a control of the quantity and temperature of air which is to provide a carrying means for removing or transporting pulverized material in suspension from the mill.

The quantity of air required to carry the pulverized material in suspension has been found to vary with the type of material, which may be coal, lime, paint pigment or similar substances,

' and must be sufllcient to transport the pulverized material in suspension without allowing it to drift or settle out in the pipe leading from the pulverizer. It is undesirable, however, to pass through the mill an excess of air over that re quired. Such an excess requires additional fan or blower capacity at its source as well as additional equipment and expense in separating the pulverized material from the carrier air at the point of usage or storage. If coal to be used as fuel is the material pulverized, then an excess of air may introduce into, the furnace a greater amount or percentage of air than is desired for efficient combustion.

I have found it desirable to control the temperature of the carrier air for such a pulverizing mill so that -the material being pulverized wilibe to ,a certain extent dried, and as in the case of fuel pulverized for combustion, any heat added to the air going with the coal to the furnace aids in the economy of operation of the furnace. Said temperatures, however, must be limited to those which are safe from an operating standpoint of the various apparatus, and with a consideration of the possibility of spontaneous combustion or volatilizing of the material.

One object of my invention is to provide a system of control for the air supplied to a pulverizer, wherein the rate of flow of the air through the pulverizer will be in desired proportion to the rate of feed of material to be pulverized.

Another object is to so arrange the system that a desirable functional relation may exist between the rate of flow of air and the rate of feed of material to the pulverizer, and with. means for manually adjusting or changing the functional relationship.

Afurther object is to so limit the minimum flow of air that it cannot be decreased below a value wherein is assured the carrying in suspension of the pulverized material.

A still further, object is to so control the temperature of the air passed through the pulverizer that the temperature of the mixture of air and pulverized material leaving the pulverizer will be as desired.

Still another object is to provide an automatic control system for combustion in a steam generating boiler combining a regulation of the input of fuel and air for combustion and to so divide the air supply that a part of it is diverted through a fuel pulverizer to provide a carrier of'the pulverized fuel to the combustion chamber:

With these and further objects in view,- I will now describe certain embodiments of my invent-ion as illustrated in the drawings.

I have chosen to illustrate and'descrlbe my invention with reference to fuel pulverizers for providing an element of combustion for a steam generating furnace or furnaces, although it-will be apparent from a study to those skilled in the art that the invention may be equally applicable to pulverizers of lime, paint pigment or other materials, which for various reasons must be ground or pulverized to a finely divided state and desirably transported by means of air to the point of usage'or of storage.

In the drawings: g V

Fig. 1 is a somewhat diagrammatic representation of a steam generating boiler with fuel and air-supplying apparatus to which the invention has been applied.

Fig. 2 is a partially sectioned elevation of a pneumatic tachometer.

Fig. 3 is a somewhat diagrammatic drawing of a fuel .pulverizer and discharge means comprising a modification for adaptation to the system illustrated in Fig. l-.

Fig. 4 is a somewhat diagrammatic illustration of a fuel pulverizer system forming a further modification of the complete control system illustrated in Fig. 1. I

Referring first to Fig. 1, I have represented generally at i a steam generating boiler, to the combustion chamber of which is supplied fuel in pulverized form, carried in suspension in a stream of air, and fed to the combustion chamber through a burner 2. A pulverizing mill 3 for reducing the fuel to a finely divided state in which it can be transported suspended in a stream of air to the boiler, is driven at a constant speed by a motor indicated at 4. Coal to be-pulverized is fed to the pulverizer 3 by a feeder 5, driven through a speed adjusting means toby an adiustable speed motor I. Air to form a carrier for the pulverized fuel and to constitute an element of combustion, is fed to the mill through a conduit Sunder pressure by a fan indicated at I driven by a constant of the invention and speed motor (not shown). I control the quantity of air flowing to the mill through the conduit 8 by the positioning in the conduit of a damper ID by a reversible means indicated in the" drawings at I I as a reversible electric motor. Air entering the fan 9 may vary in temperature, and such.

variation is controlled through the positioning of .a damper I2 by a reversible motor I3 relative to the conduits I4 and I5 wherein is available relatively hot and relatively cold air respectively.

The temperature of the stream of air carrying the suspended pulverized material to the burner 2 is indicated by a gas-filled thermostat system of which the bulb I6 is located in the path of the stream of air and pulverized material. The bulb is' connected by means of a tube I1 with a Bourdon tube I8 having an indicating arm I9 forming the movable element of a contactor for the control or positioning of the reversible motor I3. The motor Products of combustion are withrawn from the I3 is connected by the conductor 20 with the main power line 2i, and through either the conductor 23 or the conductors 24, 25 to the main power line 22.

In the circuit of the motor I3 is a two-pole, double throw switch 26, one arm of which is connected to the motor by the conductor 21 and the other by the conductor 28. In the position of rest as shown in Fig. 1, the motor is not operating, as the switch 26 is open. The switch is arranged, when moved upwardly, to connect the conductor 21 to a conductor 29 and the conductor 28 to a conductor 38, the conductors 29 and 38 forming branches of the conductor 23 through a selective push button station 3I. when the switch 26 is moved downwardly, the conductor 21 is connected to a conductor 32, and the conductor 28 to a conductor 33, the conductors 32 and 33 comprising branches ofthe conductor 24 through a selective operation in one direction or the other of the reversible motor I3 is selectively accomplished by means of the push button station 3| or by the contactor I3, in the one case'manually and in the other automatically from variations in temperature at the bulb Hi. If the switch 23 is in an upper contacting position, then the motor I3 Y may be energized in one direction or the other by means of the push button station 3| closing circuit between the conductor 23 and either the conductor 23 or the conductor 33. If the switch 26 is inits downward contacting position, then the push button station 3] is inoperative, and energization of the motor I3 may occinonly I through a closing of circuit between the confurnace by a. fan 40 driven by an adjustable speed motor 4|.

The fuel feeder motor 1, the air supply motor 33, and the motor for removing the products of combustion 4|, are connected in parallel to electrical busses 42 and 43, and are arranged to have their speed of rotation varied simultaneously through a control of the voltage supplied the busses. The bus 42 is fed from the power line 2| through a conductor 44. The bus 43 is fed from the power line 22 through a con through the conductor 25, said latter circuit controlled by a contactor 49 and periodically interrupted by the interrupting contact arm 34, previously described. The contactor 49 is arranged to close circuit for rotation of the motor 41 in one direction or the other upon a departure from a predetermined value of a factor ofthe boiler operation. In the present embodiment I have shown the contactor 48 as positioned by variations in steam pressure, effective through the pipe 50 upon a Bourdon tube 5| for positioning the contactor arm 48 in one direction orthe other when the steam pressure within the boiler l increases or decreases relative to a predetermined desired value.

It will be seen, then, that ,I have provided a means of supplying fuel and air to the boiler I for combustion, depending upon the rate of operation of the boiler, sensitive to variations in a factor of the boiler operation and intermittently eiiective through the periodic rotation of the cam 35 to minimize the tendency to hunt or overtravel. By overtraveling I mean that should steam pressurewary one pound from desired standard, the .contactor 49 might make a correction of an extent great enough to correct for one and onehalf pounds steam pressure change. The motors ductor 24 and the conductor 32 or the conductor ture temperature from a predetermined value.

The contactor I3 is effective, however, only periodically as controlled by a closing of the contact arm 34 with the conductor 24 through the periodicrotation of a cam 35 continuously rotated by a' motor 36. Thus energization of the motor I3 automatically, fromtemperature deviation, is

intermittentjor by increments, thereby allowingtime. for changesin the position of'the damper I2 to become eflective upon the-temperature at the bu'1b 'I 6 before further changesin the damper 1, 39, and would then have overtravele'd beyond the position they should haveassumed to make the proper one pound steam pressure correction. By such overtravel a correction in the opposite direction would immedifitely be necessary and it might overtravel,. thus setting up a hunting cycle. By having the circuit under the control or the contactor 43, periodically interbut if in the meantime the first increment of,

correction had satisfied the need for correction, then any additional correction, such: as might tend to cause over-travel, wouldnot 'be sent through.

1 have found that the amount offair supplied for combustion and used in its passage to'the combustion chamber as a carrier of'the pulverized fuel, should be proportioned to the amount of'i'uel being supplied, although not necessarily directly proportional thereto. With this type of apparation, when 50% fuel is supplied it might be ad visable to have 75% air, and in any event, whenever fuel is being supplied there should be a minimium rate of feed of the air great enough to prevent drifting or setting out of the fuel from the air stream, or prevent the velocity of the stream from decreasing to a point where flame could travel back' from the boiler to the mill.

Thus it will be seen that the proportion of air to fuel may be desirably different at different rates of operation, and preferably there should be provided manually adjustable means for varying the proportionality or functional relation between the supply of air and of fuel.

To properly regulate the supply of air to the mill 3, it is necessary that an'indication be obtained of the rate of flow of 'the air, and this compared to an indication of the rate of feed of fuel to be pulverized to the mill. I have found that a definite relation exists between the drop in pressure across a portion of the mill 3 and the rate of flow of air and pulverized fuel in suspension through that portion of the mill. In Fig. 1,

I have illustrated at 52 the classifying cone of themill around which the mixture passes from the grinding portion of the mill on its way to the burner 2 and across the restriction of which exists a differential pressure bearing a quadratic relation to the rate of flow of the mixture; 1. e. difierential pressure varies as the square of the rate of flow.

I have illustrated at 53 a pipe leading from the outlet of the cone to the inside of a liquid sealed bell 54 and at 55 a'pipe leading from the inlet of the cone to the inside of a liquid sealed bell 56'. The bells 54 and 56 are hung from a beam 51, pivoted intermediate the points of suspension of the bells at 58, and arranged upon oscillation across the pivot 58 to engage the contact arm 59 with either of the contacts 60 or 6|. The con-, tact arm 59 is adjustably fastened to the beam 51 in a manner such that the moment arm relation between the points of connection of the bells 54, 56 and the fulcrum 58 may be varied.

The fixedblock upon which the fulcrum 56 pivots is provided with a number of notches, each of which is adapted to engage the fulcrum 58. If it is desired to vary the moment arm relation of the bells 54, 56, the assemblyof bells and the beam 51 may be manually raised until the fulcrum 58 is free from a notch, and then said assembly moved to the right or the left and the fulcrum 58 seated in one of the other of the notches. The arm 59 may be moved along the beam 51 to adjust the centering ofthe contacts 59, 66, 6| or of the bells 54, 56, 62 relative to the pressure pipes which rise beneath them.

Tobalance against the differential pressure effective upon the bells 54 and 56, I have illustrated a liquid sealed bell 62 also suspended from the bearn' 51 and exerting a variable counterbalancing effect upon the beam. To the underside of the bell 62 is joined a pipe 62a leading from a pneumatic tachometer 64 which is driven in step with'the feeder 5 as a measure of the feeder .speed-and correspondingly, of theiate of feed of material to be pulverized to the mill.

Tn Fig.2 is shown in greater detail the pneumatic tachometer 64 wherein the driven sprocket 65 is connected to and rotates an open-ended cross tube 66 journaled in and pressure-sealed to the pipe 62a. Rotation of the sprocket 65 and of the cross tube 66 throws air by centrifugal force out of the ends of the tube 66, thus creating a suction within the pipe 62a effective upon the bell 62 to pull it downwardly and thus effect a counterbalance of the beam 51. The law of such a tachometer has been determined as a quadratic relation between speed of rotation and suction produced, so that this effect may be applied directly as a counterbalance against the similar functional relation of differential pressure between the bells 54 and 56 as an indication of the rate of flow of air through the mill.

The suction or negative pressure produced by a tachometer of this type varies directly as the square of its rotating speed. The pressure drop across the cone 52, effective beneath the bells 54, 56 also varies directly as the square of the rate offiow of air therethrough.

By properly selecting'the sizes of the bells 54,

56 and 62, as well as adjusting the fulcrum 58 for a matic tachometer 64, the desired direct or functional relation will exist between the rate of flow of air and pulverized fuel across the cone 52 and the rate of feed of material to be pulverized through the feeder 5. Deviation from such desired relation will cause the contact arm 59 to. engage either the contact point 60 or 6| to result in an energizafi-sn of the motor II in one direction or the other to correct the rate of flow of air through the mill.

The contact 6.81s connected through the conductor 1 the 11 "it 1 witch 64a, and the conductor 65a, with one prize (if a double, pole, double throw switch 66a for sexercting between push button or automatic operation of the motor The limit switch 64a is positioned by a cam 61 moved in step with the damper I0 to break circuit between the conductors 1|, 65a when a predetermined minimum damper position is reached and to prevent a further closing of the damper.

The motor II is joined to the power line 2| directly by a conductor 68 and indirectly by the conductors 69 and 18 which lead to the two arms of .the selective switch 66a. The contact 6| is joined to one pole of the switch 66a by a conductor 63: The main power line 22 is led to the switch 6611 by a conductor 14 branching through the conductors 12 and 13 and the selective push button station 15. 0

If the selective switch 66a is positioned toward the right in Fig. l, circuit will be closed through the conductors 69 and 63 to the contact 6|, and

, through the conductors 16, 65a, limit switch 64a and conductor 1| to the contact 60. Thus the motor one side ofwhich is directly connected with the power line 2| through the conductor '68, is connected for selective contact by the arm operated to connect the power line 22 through the conductor 12 to' the conductor .69, or through 76 steam pressure decreases. The decrease in steam? pressure will result in a tendency toward a counter-clockwise rotation of the contact arm 49 of the Bourdon tube to 'cause engagement with one of the terminal contacts ofthe motor 4! for a rotation thereof. The motor 41, however, will be energized only intermittently upon closure of circuit through the contact arm 34 by rotation of the cam 35. Thus, so long as the contact arm 49 engages one ofthe terminal contacts of the motor 41, the motor 47 will be operated by increments to vary the adjustment of the rheostat 48 and thereby the speed of the fuel motor I, the air supply motor 39 and the motor 4| which removes the products of combustion from the boiler. The supply of the elements of combustion to the boiler will be increased, and by increments of duration as determined by the percentage of each revolution of the cam 35 that the contact arm 34 is close circuited, and by the frequency of rotation of the cam-35. The intermittent and incremental adjustments to the speed of the fuel and air feeding motors allows time for change in the rate of feed of air and fuel to be felt at the boiler, as indicated by the steam pressure, and thus minimize the possibility of overtraveling and hunting. Should the load decrease and the pressure rise above the predetermined desirable value, the action of the contactor is the reverse, and the motors I, 38 and ll .would be decreased in speed, with a corresponding decrease in rate of feed of fuel and air forcombustion.

Considering the first condition, namely, an increase in speed of the fuel feeding motor 1 and of the feeder 5, this will result in an increase in speed of rotation of the pneumatic tachometer 84, a corresponding increase in suction within the bell 82, causing the same to move downward and oscillating the beam-51 to move the contact arm '84 is in equilibrium.

59 toward the right and close circuit with the con-'- tact point 8|, which in thp event that the switch 88a is in the 'automatic position (toward the right), will result in a rotation of the motor ll in'a direction to open the damper IQ and increase the feed of air through the conduit 8 to the mill 3, the operation of the motor ll being by increments as determined by the rotation of the cam 18. ,An'increa'se in the rate'of fiow of air through cause the contact arm 88 to seek its neutral noncontacting position wherein the relation between the pressure difierential across-the cone 52 and suction produced by the pneumatic tachometer In the arrangement illustrated in Fig. 1, the pressure transmitted through the pipes 53 and '55 will be higher than atmosphere, but it is understood that it is immaterial whether the pressures effective upon the .bells 54 and 88 are greater or less than atmosphere, as it is relativepressures or pressure difierential that produce the result.

to maintain a desired temperature of the mix-- ture of air and pulverized fuel in suspension leadingto the burner 2. Assume the selective switch 26 to be in the automatic position (downward), and that for some reaspn the temperature of the mixture passing the bulb 16 has lowered below that which is desirable, then the Bourdon tube l8 will tend to close up in a clockwise direction, moving the contact arm I8 downward, closing circuit with the conductor 33 and energizing the motor i3 in a direction to position the damper I! to open passage from the conduit II at the expense of passage from the conduit i5 and thereby admit a greater proportion of heated air to cooler air to the'conduit 8. Conversely, should the temperature at the bulb 18 increase over that desired, Bourdon tube l8 will move the contact arm l8 to close circuit with the conductor 32, and result in a rotation of the motor l3 in a direction to'cause an admission of a greater proportion of cooler air to warm air, the rotation of the motor l3 being intermittent through periodic .rotation of the cam 35.

It will be seen that both in the case of the positioning of' the damper l8 and the positioning of the damper I! for control respectively of the quantity and of the temperature of the air supplied as a carrier of the pulverized material, I have the possibility through the selective switches 26 and 68 of having either automaticcontrol or remote manualpush button control of the said dampers.

In Fig. 3 I have illustrated a modification of a fragment of the'layout shown ,in Fig. 1, like parts bearing the same reference numerals. In this mod flcation, air is supplied the mill through the conduit 8 from any desirable source, which may be the atmosphere or may be from a heater or heat-controlled device, but the control of the quantity of air supplied the mill 3 is not in the conduit 8 as is the case in Fig. 1. I have shown positioned'between the mill 3' and the burner! a fan 19driven by an adjustable speed motor I 88, exhausting from the mill 3 air and pulverized fuel carried'in suspension by the air. The pressures efiective through the pipes 53 and 55 are in this embodiment 'less than atmospheric. The control of the air flowing through the mill 3 is by speed control of the motor 88 rather than by positioning of a damper-in the conduit 8.

To control the speed of the motor 80, I have provided arheostatfl positioned by a reversible motor 82 in a manner similar to the positioning of the damper l0 bythe reversible motor H of Fig. 1.

It will be seen that my invention is equallyv applicable to pulverized material supplying systerns and pulverizing mills operated under a suction as to those operated under a pressure of the air, and whether the air isforced through the mill or drawn through the mill by an exhauster.

In Fig. 4 I have shown somewhat diagrammatically a further modification of my invention I .over that shown in Fig. 1 wherein like parts bear the same reference numerals. The. embodiment of my invention shown in Fig. 4 depicts a different type of mill, namely one commonly known as a horizontal ball mill, ascompared to the vertical ball mills of Fig. 1 and Fig. 3, and further, with somewhat dlflerent arrangements of is well known in the art. Voltages are induced control, but to accomplish a similar purpose in volume and temperature control of the air passing through the mill as a carrier for the pulverized material.

The mill 3a is rotated through the gear 83 by any suitable means (not shown), and is trunnion-mounted at the bearings 84 in a manner such that the fuel admission pipe 85 enters at one end, and the air admission conduit 8A enters at the other end, without objectionable leakage of air or pulverized material and without interfering with the free rotation of the mill 3a.

The rate of admission to the mill of coal to be pulverized is controlled by the positioning across the admission duct 85 of a gate 86 through movement of a rack 81 by a gear 88 fastened to a shaft 89. An exhauster fan 19A pulls the mixture of air and pulverized material in suspension from the mill through a conduit 98 so formed as to join the conduit 8A and an inner conduit 9I which lies within theconduit 8A and extends to the interior of the mill 3a. Air passing through the conduit 8A may pass through the mill 3a. around the conduit extension 9|, or may bypass the mill directly to the conduit 98, depending upon the positioning (vertically in the drawings) of a gate 92. All of the air entering the mill 3a around the inner conduit 9I returns through the conduit 9I with the fuel carried in suspension and passes to the exhauster 19A through the conduit 98 along with any air which has been bypassed directly from the conduit 8A to the conduit 98, depending upon the positioning of the gate 92. Thus it will be seen that if the gate 92 is in its uppermost position, none of the air from the conduit 8A'is bypassed di-,

rectly to the conduit 98, but all of said air passes to the mill and to the conduit 98 through the inner conduit 9|; whereas if the gate 92 is poturn rotated from the shaft'89.

sitioned to its lowermost position on the draw ings, then all of the air passing through the conduit 8A is bypassed directly to the conduit 98, and not having passed through the mill 3a, does nat carry any pulverized material from the mill 3a to the conduit 98.

' The gate 92 is controlled in vertical position by the rotation of a screw-threaded rod 93 in The shaft 89 is turned when desired through an energization of the motor 41A which corresponds to the motor 41 of Fig, l. The position of the gate 86, indicative of the rate of feed of fuel to the mill, and of the gate 92, both controlled by the position of the shaft 89, is in this embodiment desirably remotely indicated for comparing with the rate of flow of air to the mill, by means of self-synchronous or selsyn motors, generally 'indicated at 94 and 95. I designate at 94 a transmitting generator and at 95 a receiving motor. The transmitting generator is operated at a suitable ratio with respect to the gate 86 by means of spur gears connecting the generator shaft 96 to the shaft 89. Rotor shaft 91 of the receiving motor positions angularly an arm 98 from which is freely suspended a link 99.

The generator and motor are similar in construction, having single phase field windings, I88 and I8I on the rotors, and three-phase armature windings I82 and I83 on the stators. The field windings are energized from a suitable source of alternating current supply 2| and 22, while like points of the armature windings are interconnected.

.The operation of systems of this general char- -7& acterfor the transmission of angular movement in the three-phase stator windings of the generator and motor by the single phase field windings onthe associated rotors. When the rotors of the generator and motor are in the same an-. gular position with respect to their stators, the induced voltages in the armature windings are equal and opposite, and consequently no current is set up in the armature windings. If the rotor of the generator is turned and held in its new position, the voltages no longer counterbalance, whereby equalizing currents are caused to flow in the armature windings. The equalizing currents exert a, torque on the rotor of the motor, causing it to take up a position corresponding to the position of the generator rotor. Angular movement imparted to generator 94 is therefore reproduced by receiving motor 95.

When the shaft 89' is rotated a proportional rotation occursin angular movement of the arm 98, remotely located in the present embodiment at a point adjacent a measuring means of the rate of flow of air to the mill.

In the present embodiment I measure the air passing to the mill 3a by means of a flow nozzle I84 or other similar pressure difierentialproducing device, at opposite sides of which to the con-' duit 8A are joined the pressure pipes 53A and 55A, leading respectively to the underside of the liquid sealed bells 54A and 56A suspended from the pivoted beam 51A in a manner similar to that illustrated in Fig. 1. I desire, however, to translate the quadratic relation of, pressure difierential relative to flow, through the flow nozzle I84 to increments of flow for the positioning of the beam 51A, so I suspend from the beam 51A in addition to the bells 54A and 56A, a variable counterbalancing means'comprising a displacer I85 submerged in varying amount in a liquid such as mercury and effecting a variable counterbalancing of the differential pressure applied to the beam 51A. From the beam 51A a link I86 is freely suspended, and is positioned vertically directly in proportion to the rate of flow of air supplied to themill 3a.

Freely suspended from the lowermost ends of the vertical links 99 and I86 is a floating bar I81, from a point intermediate the ends of which is hung a link I88 joining a contact bar I89 fulcrumed intermediate its ends. The conductor II8 joins the contact bar I89 to the power line 22, and the contact bar I89 is arranged,. upon oscillation around its fulcrum, to engage and close circuit with either the contact III or the contact II2, depending upon the direction of positioning from a non-contacting neutral position. Closing the circuit with the contact III or with the contact II2'results in an operation of the motor IIA in one direction or the other for a positioning of the damper I8A to control the total supply of air to the mill. v

It will be apparent to those skilled in the art, that should the rate of feed of fuel and air to the pulverizer increase or decrease in step with each other, then the vertically suspended links 99 and I86 may be arranged to move oppositely and equally to the end that the center point of the floating bar I81 will be unchanged in poaition, and the vertical link I88 will not be moved lertically, and no rotation of the motor IIA will result, for the relationship between air and fuel is as desired. I

If, however, the rate of fuel feed is increased through movement of the motor A, then the position of the shaft 89 being remotely transmitted to cause an angular positioning of the arm 98 will move vertically the link 99 irrespective of the fact that the link I06 has not been so moved, and theresult will be a vertical positioning of the link I08 and a closing of either the contact III or the contact H2 to result in an operation of the motor IIA, varying the rate of flow of air through the conduit 8A. This change in the rate of flow of air effective across the flow nozzle I04 will change the pressure differential effective upon the bells 54A and 56A, with the result that the vertical link I06, will be positioned vertically and in opposite direction to that of the link 99. Thus when the air flow has been changed in amount in desired proportion to the rate of fuel feed, the contact arm I09 will be brought back to its original non-contacting position and further change in the position of the damper IDA will cease.

It will be seen that the modifications illustrated in Fig. 3 and Fig. 4 form modifications of a part only of the complete system illustrated in Fig. 1, and may be substituted in the complete system illustrated in Fig. 1 for the parts of which they are modifications. To save unnecessary duplication, -however, Fig. 3 and Fig. 4 havebeen drawn to illustrate only the parts'so modified rather than duplicating the complete system in each of drawings Fig. 3 and Fig. 4.

The control of heating of the air through proportioning heated air to cooled air by positioning the damper l2a relative to the ducts Ma and lia. by the motor I311 from an indication of temperature in the conduit l'la by the bulb l6a corresponds to similar arrangement of Fig. 1.

Having now describedcertain preferred em bodiments of my invention, I desire it to be understood thatI am not limited thereby, other than as claimed in view of prior art.

The present application is a division of my application, Serial No. 536,037, filedMay 8, 1931, entitled Control systems, now Patent No. 2,012,934.

What I claim as new and desire to secure by Letters Patent ofthe United States, is:-

1. A combustion control system for a steam generating boiler having a combustion chamber, comprising in combination, means for supplying fuel for combustion to the combustion chamher, a fuel pulverizer communicating with said means and including means for feeding thereinto fuelto'be pulverized, means for supplying air for combustion to the combustion chamber, control means responsive to variations from a predetermined value in a factor of the boiler operation for varying the rate of feed of the elements of combustion to the combustion chamber, means for-dividing the air supplied'and passing a portion thereof through the fuel pulverizer to constitute a carrier for the pulverized me], said control-means adapted to position saidlastnamed means whereby the amount of air pass-- ing through the fuel pulverizer will be in desired proportional relation to .said factor.

2. A combustion control system for a steamgenerating boiler having a combustion chamber, comprising in combination, means for supplying fuel for combustion to the combustion chamber,- a. fuel pulverizer communicating with said means and including means for feeding thereinto fuel .to be pulverized, means for supplying air for combustion to the combustion chamber, control means responsive to variations from a; predetermined value in a factor of the boiler operation for varying the rate of feed of theelements of quantity of air passed through the pulverizer will bear a desired functional relation to the rate of fuel fed to the combustion chamber, and means for manually adjusting said automatic means to vary said functional relation.

, 3. A combustion control system for a steam generating boiler-having a combustion chamber, comprising in combination, means for supplying fuel for combustion to the combustion chamber,

a fuel pulverizer including means for feeding thereinto fuel to be pulverized, means for supplying air for combustion to the combustion chamber, control means responsive to variations from a predetermined value in a factor of the boiler operation for varying the rate of feed of the elements of combustion to the combustion chamber, proportioning means for dividing the air supplied and passing a portion thereof through the fuel pulverizer to constitute a carrier for the pulverized fuel, and automatic means jointly responsive to the rate of feed of fuel to the pulverizer and to the rate of flow of air through the pulverizer for positioning said proportioning means whereby the quantity of air passed through the pulverizer will bear a desired functional relation to the rate of fuel fed to the combustion chamber.

4. A combustion control system for a vapor generator having a combustion chamber, comprising in combination, means for supplying fuel for combustion to the combustion chamber, a fuel pulverizer communicating with said means and including. means for feeding thereinto fuel to be pulverized, means for supplying air for combustion to the combustion chamber, control means responsive to variations from a predetermined value in a variable of the generator operation combustion to the combustion chamber, means for continuously passing'a portion of the air supplied for combustion through the. fuel puiverizer to constitute a carrier for the pulverized fuel, and automatic means jointly responsive to for varying the rate of feed of the elements of the rate of feed of fuel to the pulverizer and to the rate of flow of air through the pulverizer for continuously regulating the quantity of carrier air. i

5. A combustion control system for a vapor generator having a combustion chamberfcomprising in combination, means for supplying fuel for combustion to the combustion chamber, a fuel pulverizer including means for feeding thereinto fuel to be pulverized, means for supplying air for combustion to the combustion chamber, control means responsive to variations from a predetermined value in a variable of the generator operation for varying the rate of feed of the elements of combustion to the combustion chamber, means for continuously passing a portion of the air supplied for combustion throughthe fuel pulverizer to constitute a carrier for the pulverized fuel, automatic means jointly responsive to the rate of-feed of fuel to the pulverizer and to the rate of'fiow of air through the pul- -verizer for continuously regulating thequantity of carrier air, and means responsive to the temperature of the air and fuel in suspension leav amigos ing the pulverizer for regulating the temperature of the air passing through the pulverizer.

6. A combustion control system for a vapor generator having a combustion chamber, means for supplying fuel for combustion to the chamher, a fuel pulverizer communicating with said means and including means for feeding thereinto fuel to be pulverized, means for supplyingbe pulverized, means jointly responsive to the .20 rateof feed of fuel to the pulverizer and to the rate of flow of air to the pulverizer for positioning said proportioning means whereby the quantity of air passed through the pulverizer will bear a desired functional relation to the rate of fuel feed to the pulverizer.

'7. A combustion control system for a vapor generator having a combustion chamber, means I for supplying fuel for combustion to the chamber,. a fuel pulverizer communicating with said means including means for feeding ,thereinto fuel to be pulverized, control means responsive to variationsfrom a predetermined value of a condition of the vapor forregulating the feed of 'fuel to said pulverizer, means for supplying air to the pulverizer to providea carrier for the pulverized, fuel, regulating means for said last \named means, means -for determining the flow of carrier air, means for determining the rate of supply of fuel to the pulverizer, and means under the joint control of said last two named means for positioning said regulating means.

8. A combustion control system for a. vapor generator having a combustion chamber, means for supplying fuel for combustion to the chamber, a fuel pulverizer communicating with said means and including means for feeding thereinto fuel to be rpulverized, control means responsive to variations from a predetermined value of a condition of the vapor produced by said generator for regulating the feed of fuel to the pulverizer, means'for passing air through the pulverizer to constitute a carrier for the pulverized fuel from the pulverizer to the combustion chamber means for varying the flow of said carrier air, and means responsive to the rate of fuel feed to the pulverizQ for controlling said last named means to maintain a desired proportionallty between the rate of flow of carrier airv and rate of fuel feed to the pulverizer.

generator having a combustion chamber, means for-supplying fuel for combustion to the chamber, a fuel pulverizer communicating with said means and including means for feeding thereinto fuel to be pulverized, control means responsive'to variations from a, predetermined value of a condition of the vapor produced by said generator for regulating the feed of fuel to the pulverizer, means for passing air through the fuel pulverizer to constitute a carrier for the pulverized fuel from the pulverizer to the combustion chamber, means for varying the flow of said carrier air, means responsive to the rate of fuel feed to the pulverizer for controlling said last named means to maintain a desired proportionality between the rate of flow of carrier air and rate of fuel feed to the pulverizer, and thermostatically controlled -means for maintaining a presuspensionleaving the pulverizer.

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9. A combustion control system for a vapor 

